Sec-butyl acetate is also called as secondary butyl acetate, which is one of the four isomers of butyl acetate. Sec-butyl acetate is an inflammable, colorless liquid with fruity odor, and the property of the sec-butyl acetate is similar to other isomers in most situations. Various resins and organic compounds can be dissolved into the sec-butyl acetate. The boiling point of the sec-butyl acetate is lower than those of n-butyl ester and isobutyl ester which are commonly used, and the evaporation rate of the sec-butyl acetate is faster. Therefore, it is mainly used as a solvent, reaction medium, extracting agent composition, metal cleaning agent, and fruit perfume, and it is also used in medical and pharmaceutical industry.
Compared with traditional processes of producing sec-butyl acetate, the process of using 1-butene and 2-butene as raw materials to react with acetic acid has advantages of wide raw material sources, good economic benefits and being environment-friendly. Therefore, lots of researchers pay close attention to the above synthesis process, nevertheless, the research on separation and purification process of the above reaction is less reported.
A method for producing sec-butyl acetate is disclosed in U.S. Pat. No. 5,457,228, which uses acetic acid to react with 1-butene and 2-butene, and has a relatively high olefin conversion ratio and products selectivity. With regard to the separation process, it refers that the sec-butyl acetate can be separated from the reaction mixture with distillation, but no concrete separation process is disclosed. Accordingly, the purity of the products after separation isn't disclosed, either.
The inventors of the present application have disclosed a method of separating sec-butyl acetate from the reaction mixtures of the reaction between acetic acid and butene or mixed C4 in Chinese Patent Application No. CN 200710200148X, which comprises the steps of (1) feeding the reaction mixture produced in the reaction of acetic acid and mixed C4 into a flash tower, and removing the remaining mixed C4 and light component from the top of the flash tower by flash evaporation; (2) feeding the reaction products from the bottom of the flash tower into an azeotropic distillation tower, adding an azeotropic agent A, and separating sec-butyl acetate from acetic acid by azeotropic distillation; (3) feeding the materials from the top of the azeotropic distillation tower into a purification tower, and obtaining the sec-butyl acetate by distillation; (4) when the amount of the azeotropic agent A contained in acetic acid obtained from the lower part of the azeotropic distillation tower has effects on carrying out the reaction, catalytic activity, or catalyst lifetime, feeding the materials from the lower part of the azeotropic distillation tower into an acid concentrating tower, adding azeotropic agent B, then concentrating the acetic acid by another azeotropic distillation and recycling the concentrated acetic acid, or when the amount of the azeotropic agent A contained in acetic acid obtained from the lower part of the azeotropic distillation tower has no effects on carrying out the reaction, catalytic activity, and catalyst lifetime, recycling the materials from the lower part of the azeotropic distillation tower directly to the reaction system.
In the above process of producing sec-butyl acetate with raw materials of acetic acid and butene or mixed C4, it does not mention that in raw materials the butene or mixed C4 will polymerize to form heavy hydrocarbon. In addition, it does not refer to the methods of separating and removing acetic acid, sec-butyl acetate and heavy hydrocarbon from reaction mixtures.